274 



MANUAL OF ZOOLOGY 



SECT. 



cavity, and out at the exhalant siphon. The ingoing cur- 

 rent carries with it not only oxygen for the aeration of the 



A 



Fig. 163. — Anodonta cygnea. A, transverse section of outer; B, of inner gill; 

 C, diagram of gill-structure; D, transverse section of gill-filament, b.c, blood- 

 corpuscle; b. v, blood-vessels; ch, chitin; /, branchial filaments; e/, epithelium; 

 i./.j, inter-filamental junction; i. /, inner lamella; i. /.y, inter-lamellar junction; 

 0. I, outer lamella; os, external ostium; os' , internal ostium; r, chitinous rods; 

 ■w. t, water tubes. (A, B, and D, after Peck.) 



blood, but also diatoms, Infusoria, and other microscopic 

 organisms, which are swept into the mouth by the cilia cov- 



